Image forming apparatus, shared machine, image forming system, and control method of image forming apparatus

An image forming apparatus includes: a display controller that displays an operation screen including a function button for executing a function on a display section; a press determination section that determines whether the function button is short pressed or long pressed; when the press determination section determines that the function button is short pressed, a function execution section that executes the function; and when the press determination section determines that the function button is long pressed, an execute privilege setting section that sets an execute privilege of the function from a plurality of types of execute privileges in accordance with a long press time of the function button.